Use off-heap data for type feedback in PolymorphicInstanceCallInstr

runtime/vm/weak_code.cc

Index: runtime/vm/weak_code.cc
diff --git a/runtime/vm/weak_code.cc b/runtime/vm/weak_code.cc
index c7e12d14c5b7156463feacf0c06c6a9ab3a6a2f4..3b771f4bbced045de0c2810fb3757dc719ffab07 100644
--- a/runtime/vm/weak_code.cc
+++ b/runtime/vm/weak_code.cc
@@ -22,8 +22,12 @@ void WeakCodeReferences::Register(const Code& value) {
   if (!array_.IsNull()) {
     // Try to find and reuse cleared WeakProperty to avoid allocating new one.

[Vyacheslav Egorov (Google), 2017/04/10 10:59:28]

You need to amend the comment because the code below does more than what this
comment states - because you changed how the array grows.

Additionally please reflect this change in the CL description (maybe with
rationale).

[erikcorry, 2017/04/19 15:06:41]

Moved to different CL

     WeakProperty& weak_property = WeakProperty::Handle();
-    for (intptr_t i = 0; i < array_.Length(); i++) {
+    for (intptr_t i = array_.Length() - 1; i >= 0; i--) {
       weak_property ^= array_.At(i);
+      if (weak_property.raw() == WeakProperty::null()) {
+        weak_property ^= WeakProperty::New(Heap::kOld);
+        array_.SetAt(i, weak_property);
+      }
       if (weak_property.key() == Code::null()) {
         // Empty property found. Reuse it.
         weak_property.set_key(value);
@@ -37,8 +41,8 @@ void WeakCodeReferences::Register(const Code& value) {
   weak_property.set_key(value);
 
   intptr_t length = array_.IsNull() ? 0 : array_.Length();
-  const Array& new_array =
-      Array::Handle(Array::Grow(array_, length + 1, Heap::kOld));
+  const Array& new_array = Array::Handle(
+      Array::Grow(array_, length + 1 + (length >> 2), Heap::kOld));
   new_array.SetAt(length, weak_property);
   UpdateArrayTo(new_array);
 }
@@ -52,7 +56,8 @@ bool WeakCodeReferences::IsOptimizedCode(const Array& dependent_code,
   WeakProperty& weak_property = WeakProperty::Handle();
   for (intptr_t i = 0; i < dependent_code.Length(); i++) {
     weak_property ^= dependent_code.At(i);
-    if (code.raw() == weak_property.key()) {
+    if (weak_property.raw() != WeakProperty::null() &&
+        code.raw() == weak_property.key()) {
       return true;
     }
   }
@@ -88,6 +93,9 @@ void WeakCodeReferences::DisableCode() {
   Function& function = Function::Handle();
   for (intptr_t i = 0; i < code_objects.Length(); i++) {
     weak_property ^= code_objects.At(i);
+    if (weak_property.raw() == WeakProperty::null()) {
+      continue;
+    }
     code ^= weak_property.key();
     if (code.IsNull()) {
       // Code was garbage collected already.